1. Articles from Janarthanan Rasakanthan

    1-7 of 7
    1. Advances in characterisation, calibration and data processing speed of optical coherence tomography systems (Thesis)

      Advances in characterisation, calibration and data processing speed of optical coherence tomography systems (Thesis)

      This thesis describes advances in the characterisation, calibration and data processing of optical coherence tomography (OCT) systems. Femtosecond (fs) laser inscription was used for producing OCT-phantoms. Transparent materials are generally inert to infra-red radiations, but with fs lasers material modification occurs via non-linear processes when the highly focused light source interacts with the materials. This modification is confined to the focal volume and is highly reproducible. In order to select the best inscription parameters, combination of different inscription parameters were tested, using three fs laser systems, with different operating properties, on a variety of materials. This facilitated the understanding of ...

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    2. Feature Of The Week 9/22/13: Lehigh University Researchers Investigate Space-Division Multiplexing for High-Speed Optical Coherence Tomography

      Feature Of The Week 9/22/13: Lehigh University Researchers Investigate Space-Division Multiplexing for High-Speed Optical Coherence Tomography

      High speed, high resolution and high sensitivity are desirable for optical coherence tomography (OCT). Here, we demonstrate a space-division multiplexing (SDM) technology that translates long coherence length of a commercially available wavelength tunable laser into high OCT imaging speed. We achieved an effective 800,000 A-scans/s imaging speed using a commercially available 100,000 Hz tunable vertical cavity surface-emitting laser (VCSEL) from Thorlabs Inc. A sensitivity of 94.6 dB and a roll-off of < 2 dB over ~30 mm imaging depth were measured in the prototype SDM-OCT system. An axial resolution of ~11 m in air (or ~8.3 ...

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    3. Space-division multiplexing optical coherence tomography

      Space-division multiplexing optical coherence tomography

      High speed, high resolution and high sensitivity are desirable for optical coherence tomography (OCT). Here, we demonstrate a space-division multiplexing (SDM) technology that translates long coherence length of a commercially available wavelength tunable laser into high OCT imaging speed. We achieved an effective 800,000 A-scans/s imaging speed using a 100,000 Hz tunable vertical cavity surface-emitting laser (VCSEL). A sensitivity of 94.6 dB and a roll-off of < 2 dB over ~30 mm imaging depth were measured from a single channel in the prototype SDM-OCT system. An axial resolution of ~11 μm in air (or ~8.3 μm ...

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    4. Fabrication of high quality optical coherence tomography (OCT) calibration artefacts using femtosecond inscription

      Fabrication of high quality optical coherence tomography (OCT) calibration artefacts using femtosecond inscription

      Optical coherence tomography (OCT) is a non-invasive three-dimensional imaging system that is capable of producing high resolution in-vivo images. OCT is approved for use in clinical trials in Japan, USA and Europe. For OCT to be used effectively in a clinical diagnosis, a method of standardisation is required to assess the performance across different systems. This standardisation can be implemented using highly accurate and reproducible artefacts for calibration at both installation and throughout the lifetime of a system. Femtosecond lasers can write highly reproducible and highly localised micro-structured calibration artefacts within a transparent media. We report on the fabrication of ...

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    5. Three-dimensional calibration targets for optical coherence tomography

      Three-dimensional calibration targets for optical coherence tomography

      The recent expansion of clinical applications for optical coherence tomography (OCT) is driving the development of approaches for consistent image acquisition. There is a simultaneous need for time-stable, easy-to-use imaging targets for calibration and standardization of OCT devices. We present calibration targets consisting of three-dimensional structures etched into nanoparticle-embedded resin. Spherical iron oxide nanoparticles with a predominant particle diameter of 400 nm were homogeneously dispersed in a two part polyurethane resin and allowed to harden overnight. These samples were then etched using a precision micromachining femtosecond laser with a center wavelength of 1026 nm, 100kHz repetition rate and 450 fs ...

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    6. Femtosecond laser micro-inscription of optical coherence tomography resolution test artifacts

      Femtosecond laser micro-inscription of optical coherence tomography resolution test artifacts
      Optical coherence tomography (OCT) systems are becoming more commonly used in biomedical imaging and, to enable continued uptake, a reliable method of characterizing their performance and validating their operation is required. This paper outlines the use of femtosecond laser subsurface micro-inscription techniques to fabricate an OCT test artifact for validating the resolution performance of a commercial OCT system. The key advantage of this approach is that by utilizing the nonlinear absorption a three dimensional grid of highly localized point and line defects can be written in clear fused silica substrates.
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    7. Processing and rendering of Fourier domain optical coherence tomography images at a line rate over 524 kHz using a graphics processing unit

      Processing and rendering of Fourier domain optical coherence tomography images at a line rate over 524 kHz using a graphics processing unit
      In Fourier domain optical coherence tomography (FD-OCT), a large amount of interference data needs to be resampled from the wavelength domain to the wavenumber domain prior to Fourier transformation. We present an approach to optimize this data processing, using a graphics processing unit (GPU) and parallel processing algorithms. We demonstrate an increased processing and rendering rate over that previously reported by using GPU paged memory to render data in the GPU rather than copying back to the CPU. This avoids unnecessary and slow data transfer, enabling a processing and display rate of well over 524,000 A-scan/s for a ...
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    1-7 of 7
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  2. Topics in the News

    1. (7 articles) Janarthanan Rasakanthan
    2. (4 articles) Kate Sugden
    3. (3 articles) Peter D. Woolliams
    4. (3 articles) Pete H. Tomlins
    5. (3 articles) Aneesh Alex
    6. (2 articles) Lehigh University
    7. (2 articles) UK National Physical Laboratory
    8. (2 articles) Chao Zhou
    9. (1 articles) University of London
    10. (1 articles) Wolfgang Drexler
    11. (1 articles) Institute of Applied Physics
    12. (1 articles) Medical University of Vienna
    13. (1 articles) Kyungpook National University
    14. (1 articles) Singapore Eye Research Institute
    15. (1 articles) University of Western Australia
    16. (1 articles) Stefan G. Sacu
    17. (1 articles) Brendan F. Kennedy
    18. (1 articles) Yongyang Huang
    19. (1 articles) Jeehyun Kim
    20. (1 articles) Ursula Schmidt-Erfurth
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    Processing and rendering of Fourier domain optical coherence tomography images at a line rate over 524 kHz using a graphics processing unit Femtosecond laser micro-inscription of optical coherence tomography resolution test artifacts Three-dimensional calibration targets for optical coherence tomography Fabrication of high quality optical coherence tomography (OCT) calibration artefacts using femtosecond inscription Space-division multiplexing optical coherence tomography Feature Of The Week 9/22/13: Lehigh University Researchers Investigate Space-Division Multiplexing for High-Speed Optical Coherence Tomography Advances in characterisation, calibration and data processing speed of optical coherence tomography systems (Thesis) Full-range space-division multiplexing optical coherence tomography angiography Measuring 3D Optic Nerve Head Deformations using Digital Volume Correlation of in vivo Optical Coherence Tomography Data (Thesis) Optical coherence tomography for characterization of nanocomposite materials (Thesis) In Vivo Corneal Microstructural Changes in Herpetic Stromal Keratitis: A Spectral-Domain Optical Coherence Tomography Analysis Non-invasive optical screening of Streptococcus Pneumonia based inflammatory changes of the tympanic membrane and mastoid mucosa in guinea pig otitis media using optical coherence tomography